Acid gas removal processes are widely used in the gas processing industries to separate acid gas from sour gas, such as synthesis gas (hereinafter “syngas”), natural gas, or other process gases that contain acid gas. For example, syngas streams can be produced by gasification of coal, coke, or heavy hydrocarbon oils. Some examples of acid gases are hydrogen sulfide (H2S), carbonyl sulfide (COS), and other sulfur compounds, carbon dioxide (CO2), and hydrogen cyanide (HCN). By separating the acid gases, the syngas stream is made more suitable for combustion and/or further processing.
One conventional approach for removing acid gas from sour gas uses a physical solvent (i.e., absorbent solvent) in countercurrent contacting flow with a sour gas stream. Physical solvents, unlike chemical solvents, do not involve chemical reactions for acid gas removal but rather involve a physical mechanism(s), such as absorption, for acid gas removal. Some examples of physical solvents include n-methyl-2-pyrrolidone, methanol, propylene carbonate, and the like. Additionally, the acid gas absorption capacity of many physical solvents favors lower temperatures.
During countercurrent contacting flow, acid gas from the sour gas is absorbed into the physical solvent, which is in the liquid phase, to form a treated gas stream that is substantially free of acid gas and a loaded physical solvent stream that is partially or substantially saturated with the acid gas. Depending upon the vapor pressure of the physical solvent, some of the physical solvent may be entrained in the treated gas stream. Physical solvents are generally expensive and can cause damage to downstream equipment for further processing of the treated gas stream. As such, it is desirable to recover the physical solvent that is entrained in the treated gas stream. Unfortunately, current approaches for recovering the entrained physical solvent are not necessarily feasible at lower temperatures that otherwise may favor improved acid gas absorption.
Accordingly, it is desirable to provide apparatuses and methods for removing acid gas from sour gas using an absorbent solvent with improved acid gas absorption. Additionally, it is desirable to provide apparatuses and methods for removing acid gas from sour gas using an absorbent solvent to form a treated gas stream and for recovering entrained absorbent solvent in the treated gas stream. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.